Phacoemulsification Cataract Surgery Safe to Perform in COVID-19 Pandemic

Phacoemulsification cataract surgery is the most commonly performed surgical procedure in the ophthalmic set-up. Though the prevalence of the virus in the conjunctiva and ocular fluids is low and the risk of transmission is controversial, recommendations to postpone elective cataract surgery were issued considering the potential of the procedure to generate and disseminate aerosol.

In this recent study, phacoemulsification was performed in an experimental set-up, on enucleated goat eyes and cadaveric human corneoscleral rims mounted on an artificial anterior chamber. The basic experiment was as follows:

1. The enucleated goat eyes were mounted on a mannequin head and the human corneoscleral button was kept on a Barron artificial chamber attached to a syringe filled with balanced salt solution. The purpose was to create a model which could simulate the scenario of phacoemulsification in the human eye.
2. The Visalis 100 (Carl Zeiss Meditec AG), a peristaltic pump device with titanium straight tips was used for the procedure.
3. The sculpt (80 mm Hg vacuum, 18 mL/min flow rate, and 40 µm of ultrasound) and quadrant removal modes (350 mm Hg vacuum, 34 mL/min flow rate, and 60 μm ultrasound) were used in linear and fixed modes.
4. Longitudinal or axial mode of phacoemulsification was used instead of the torsional mode so that the heat build-up would be greater with increased propensity of aerosol generation.
5. Both microincision and standard phacoemulsification surgeries were performed using straight tips of 2.2 mm and 2.8mm diameter such that the main incision would be either equal to or larger than the sleeve size.
6. Nucleus management using sculpt and quadrant removal mode was done by embedding the phacoemulsification tip inside the nucleus. The process was repeated after exposing the phacoemulsification tip and keeping it close to the ocular surface.
7. High-speed shadowgraphy technique was used to detect the generation of any droplets and aerosols.

The results of the experiment were similar in the goat eyes and the human corneoscleral rims mounted on artificial chamber.

1. There was no aerosol generation during phacoemulsification in a closed chamber when the sleeve tip and incision were of the same size.
2. When the incision size was greater than the sleeve tip size, leakage of fluid from the main incision was seen on shadowgraphy but there was still no generation of aerosol.
3. The explanation offered by the authors is that the exposed part of the tip was near the centre of the eye and in direct contact with the nucleus. The part in contact with the wound was cushioned by the sleeve, and the continuous flow of liquid on its side dissipated all the heat that was generated.
4. Aerosol was generated only when the exposed tip came in contact with the liquid film on the corneal surface resulting in atomisation of the fluid by the generated heat. However, the aerosols had a nominal droplet size of 50 microns and travel distance of 1.3m which are insufficient for transmission of infection from the patient to the operating surgeon, nurse or technicians in the operating room. Moreover, this does not simulate the scenario of phacoemulsification which is essentially done within the anterior chamber.

The study thus concluded that phacoemulsification is a safe procedure with minimal or no aerosol generation and may be performed with the universally recommended precautions during the COVID pandemic. The authors further recommend the treatment of the ocular surface with povidone iodine for 2 minutes prior to cataract surgery to reduce the viral load in the conjunctiva and tear film. Use of similar-sized phacoemulsification tip, sleeve, and incision, and application of ultrasound power only after the tip is completely inside the anterior chamber have been suggested to further minimise aerosol generation.

For the full article, click on the link

https://journals.lww.com/jcrs/Fulltext/2020/09000/Propensity_and_quantification_of_aerosol_and.15.aspx